Problema Solution
Greg's cell phone plan charges a fixed monthly fee, plus an amount for each minute over the number of minutes included with the plan. Last month, Greg went over by 38 minutes, and the bill was $57.10 This month, Greg went over by 84 minutes, and the bill was $77.80
1) Determine the rate of change for Cell Phone Company A?
2) Determine the equation of the line for Cell Phone Company A?
Answer provided by our tutors
1)
let fixed charge be $c and charges per minutes be $m
then from given info we have
57.10 = c + 38m and 77.80 = c + 84m
now substract 1st from 2nd,
20.70 = 46m
== > m = $20.70/46 = $0.45
hence, rate of change is $0.45
2)
from equation 1, we get
57.10 = c + 38*0.45
==> c = 57.10 - 17.10 = 40
hence, equation of line is
y = 0.45x + 40
where x denotes minutes and y denotes bill amount